NICET Special Hazards III cheat sheet

Clean agent total-flooding design concentration must be at least the NOAEL-adjusted extinguishing concentration; for Class C hazards the design concentration may not exceed the NOAEL, and for occupied spaces the worst-case exposure must stay below the NOAEL (NFPA 2001).

NFPA 2001 hold time: the agent concentration must remain at or above the design concentration for the period needed for occupant egress and for re-ignition control, with the minimum design hold time typically 10 minutes unless a documented risk analysis justifies otherwise.

FM-200 (HFC-227ea) design concentrations commonly range 6.25% to 7.0% for Class A and 7.0% to 8.0% for Class B; NOAEL is 9.0%, so Class C designs must not exceed 9.0%.

Inergen (IG-541) design concentrations typically run 34% to 38% for Class A and up to 43% for Class B; NOAEL is 43%, so Class C designs must not exceed 43%.

Novec 1230 (FK-5-1-12) design concentration is typically 4.2% to 5.0% for Class A and up to 5.85% for Class B; NOAEL is 10%, giving a wide safety margin.

CO2 total-flooding for occupied spaces is prohibited; CO2 is permitted only in unoccupied spaces, normally with lockout/tagout and pre-discharge alarm, and design concentration is typically 34% or higher.

For inert-gas systems, the agent quantity is calculated using the ideal gas relation: agent mass = (volume of enclosure x design concentration x gas density) / (1 - design concentration), with altitude correction for the enclosure volume.

Halocarbon agent quantity uses the NFPA 2001 formula: W = (V/S) x (C/(100-C)), where W is agent mass, V is enclosure volume, S is the specific vapor volume at the design temperature, and C is the design concentration in percent.

Pre-discharge alarm and time delay: NFPA 2001 requires a distinctive alarm and a time delay (commonly 30 seconds, adjustable) before discharge in occupied areas to allow egress, with abort stations provided where occupants may need to stop discharge.

Clean agent total-flooding design concentration must be at least the NOAEL-adjusted extinguishing concentration; for Class C hazards the design concentration may not exceed the NOAEL, and for occupied spaces the worst-case exposure must stay below the NOAEL (NFPA 2001).

NFPA 2001 hold time: the agent concentration must remain at or above the design concentration for the period needed for occupant egress and for re-ignition control, with the minimum design hold time typically 10 minutes unless a documented risk analysis justifies otherwise.

FM-200 (HFC-227ea) design concentrations commonly range 6.25% to 7.0% for Class A and 7.0% to 8.0% for Class B; NOAEL is 9.0%, so Class C designs must not exceed 9.0%.

Inergen (IG-541) design concentrations typically run 34% to 38% for Class A and up to 43% for Class B; NOAEL is 43%, so Class C designs must not exceed 43%.

Novec 1230 (FK-5-1-12) design concentration is typically 4.2% to 5.0% for Class A and up to 5.85% for Class B; NOAEL is 10%, giving a wide safety margin.

CO2 total-flooding for occupied spaces is prohibited; CO2 is permitted only in unoccupied spaces, normally with lockout/tagout and pre-discharge alarm, and design concentration is typically 34% or higher.

For inert-gas systems, the agent quantity is calculated using the ideal gas relation: agent mass = (volume of enclosure x design concentration x gas density) / (1 - design concentration), with altitude correction for the enclosure volume.

Halocarbon agent quantity uses the NFPA 2001 formula: W = (V/S) x (C/(100-C)), where W is agent mass, V is enclosure volume, S is the specific vapor volume at the design temperature, and C is the design concentration in percent.

Pre-discharge alarm and time delay: NFPA 2001 requires a distinctive alarm and a time delay (commonly 30 seconds, adjustable) before discharge in occupied areas to allow egress, with abort stations provided where occupants may need to stop discharge.